WO2001060541A1

WO2001060541A1 - Method and device for detecting plate thickness in press

Info

Publication number: WO2001060541A1
Application number: PCT/JP2001/001081
Authority: WO
Inventors: Kazuhiro Kanno
Original assignee: Amada Company, Limited
Priority date: 2000-02-18
Filing date: 2001-02-15
Publication date: 2001-08-23
Also published as: US6826939B2; US20030019266A1; TW558459B

Abstract

A method of detecting a plate thickness, comprising the steps of detecting a pressure in a rod side cylinder chamber (19) of a hydraulic cylinder (13R) allowing a ram (5U) to be lowered by its own weight and moved vertically by a hydraulic pressure detecting means (21), detecting, by a judgment part (65), a position of a punch (P) installed on the ram (5U) in contact with the upper surface of a work (W) based on a variation in the detected pressure and, after the upper surface of the work (W) is detected, calculating, by a plate thickness calculation part (67), the plate thickness of the work (W) based on the upper surface position of a die (D) identified beforehand and stored in a memory (63).

Description

Specification

Thickness detection method and thickness detection device for press machine

The present invention relates to a sheet thickness detecting method and a sheet thickness detecting apparatus for a press machine that presses a work by cooperation of a punch and a die. Background art

As a conventional sheet thickness detecting device in a press machine, particularly in a press brake, for example, Japanese Patent Application Laid-Open No. H10-18080

Some are described in No. 499. In this press brake, the torque of the servomotor that drives the hydraulic pump that supplies hydraulic oil to the hydraulic cylinder for driving the ram changes, and the pinch in which the upper die contacts the workpiece is changed. A point has been detected.

However, in the plate thickness detection method that detects the pitching point from the change in the pressure on the pressurized side of the hydraulic cylinder, the cross-sectional area of the cylinder chamber is large. (Pressure on the cylinder head) While pressurizing, the change point where the pressure rises is detected, so it is difficult to catch the pressure change point especially when the press machine becomes larger. There is a problem.

In addition, since the pressurized side is pressurized, if the detection of the pinching point is delayed, the work will bend due to the pressing force acting on it, and it will not be possible to accurately detect the thickness of the sheet overnight. The problem is is there.

The present invention has been made by focusing on the problems of the conventional technology as described above.The purpose of the present invention is to detect an accurate thickness without bending a workpiece. An object of the present invention is to provide a method for detecting a thickness of a press machine and a device for detecting the thickness of the press machine. Disclosure of the invention

In order to achieve the above object, a method for detecting a thickness of a press machine according to the present invention using a first aspect includes the following steps: The ram is positioned at a certain height. From the cylinder; detects the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time; and detects a punch from the change in the detected pressure. Detects when it comes into contact with the workpiece; Detects the vertical position of the ram at this time; Detects the height of the ram and the height of the pressure that is known in advance and the top of the die. The thickness of the workpiece is determined from the set height of the workpiece; and, based on the determined thickness of the workpiece, the work is performed in cooperation with the punch and die by vertically moving the ram on which the punch is mounted. Press working.

Therefore, the ram is lowered from a certain height to detect the top position of the workpiece, which is the reference when detecting the thickness of the workpiece. Detects the pressure of hydraulic oil discharged from the cylinder chamber on the rod side of the cylinder, and is attached to the ram based on the detected change in pressure. Since the position where the punch abuts on the workpiece is detected, the change in the ram position is more sensitive than when detecting the pressure in the cylinder chamber on the head side of the cylinder with a large cross-sectional area. To detect. Then, when the upper surface of the work is detected, the thickness of the work is calculated from the detected upper surface position, a predetermined height of the ram, and a set height based on the upper surface position of the die. Can be.

The method for detecting a thickness of a press machine according to the invention based on the second aspect subordinate to the first aspect includes, in the method, lowering the ram by its own weight; Detects the pressure of hydraulic oil discharged from the cylinder chamber on the mouth side; and detects when the punch abuts on the workpiece from the change in the detected pressure.

In the above configuration, when the ram on which the punch is mounted is lowered by its own weight, and the punch comes into contact with the workpiece due to the change in the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time. Is detected. During the lowering of the ram, there is no pressurization of the hydraulic oil into the cylinder chamber on the cylinder head side, and the suction is performed by the negative pressure generated by the lowering of the piston.

Accordingly, even if the detection of the contact of the punch with the work is delayed, only the own weight of the ram or the like acts on the work, and the work can be prevented from bending.

The method for detecting a thickness of a press machine according to the invention according to the third aspect, which is dependent on the first or second aspect, comprises the steps of: Then, lower the ram so that it does not bend even if the punch touches the work, at a speed less than the maximum gravity falling speed.

Therefore, when the ram falls under its own weight, the ram will not bend even if the nose hits the work due to the fall of the ram. Since it falls, the work can be prevented from bending even when it comes into contact with the non-working workpiece.

A method for detecting a plate thickness of a press machine according to a fourth aspect of the invention, which is dependent on any of the first to third elements, comprises: When the pressure of the hydraulic oil discharged from the cylinder chamber changes from the pressure of its own weight to the atmospheric pressure, it is detected as when the punch touches the work.

In the above configuration, the pressure of the hydraulic oil discharged from the rod-side cylinder chamber detected when the ram is lowered is the pressure accompanying the lowering of the ram and the punch due to its own weight. When the punch comes into contact with the work, the pressure due to its own weight disappears, and the atmospheric pressure is detected. Therefore, when this atmospheric pressure is detected, it can be determined that the punch has contacted the work.

A fifth aspect of the invention for a method of detecting a thickness of a press machine according to the invention includes the following steps: controlling a descent speed of a ram from a certain height position; To detect the lowering position of the ram; detect the stop position of the ram from the detected change in the ram position; Is determined to be the position where the punch touches the workpiece on the die; the ram position determined to be in contact with the workpiece and the predetermined height and the upper surface of the die which are known in advance. The thickness of the work is determined from the set height of the difference; and, based on the determined thickness of the work, the ram on which the punch is mounted is moved up and down, and the punch and the die are moved. Press work of the work in cooperation with

Therefore, in order to detect the upper surface position of the workpiece, which is a reference when detecting the thickness of the workpiece, the ram is lowered from a certain height by controlling the descending speed, Since the stop position is detected from the change in the descent position of the cylinder and this stop position is determined to be the top surface of the work, the pressure in the cylinder chamber on the cylinder side with a large cross-sectional area of the cylinder chamber The change in the ram position can be detected more sensitively than in the case of detection. Then, when the upper surface of the workpiece is detected, the set height of the difference between the upper surface position of the work and a predetermined height of the ram and a predetermined upper surface position of the die is determined. The work thickness can be calculated based on the

A thickness detecting apparatus for a press machine according to a sixth aspect of the present invention includes the following: a ram position detecting means for detecting a vertical position of a ram on which a punch is mounted; Hydraulic pressure detecting means for detecting the pressure of the hydraulic oil discharged from the rod-side cylinder chamber of the hydraulic cylinder of the hydraulic cylinder: from the pressure change detected by the hydraulic pressure detecting means, A determination unit for detecting a position where the punch abuts on the park; and The position of the ram at the time when it is determined that the punch has contacted the workpiece is determined from the predetermined height of the ram, which is known in advance, and the set height of the difference between the upper surface of the die and the ram. A thickness calculating unit for calculating the thickness of the workpiece; thereby, the ram is moved up and down by a hydraulic cylinder, and the workpiece is pressed in cooperation with a nonch and a die. I do .

Therefore, in order to detect the upper surface position of the workpiece, which is the reference when detecting the thickness of the work, the hydraulic cylinder is used to move the ram up and down by the hydraulic pressure detecting means. The pressure of the hydraulic oil discharged from the Linden chamber is detected, and the judging section detects the position where the punch attached to the ram contacts the work from the detected change in the pressure. At this time, the vertical position of the ram is detected by the ram position detecting means, which is different from the case of detecting the pressure in the cylinder chamber on the head side where the cross-sectional area of the cylinder chamber is large. Also sensitively detects changes in the ram position. When the upper surface of the work is detected, the thickness calculator calculates the thickness of the work based on the set height of the difference between the fixed height of the ram and the upper surface of the die, which is known in advance. Is calculated.

The sheet thickness detecting device for a press machine according to the invention based on the seventh aspect, which is dependent on the sixth aspect, further includes: when lowering the ram by its own weight, A ram that calculates the maximum drop speed of its own weight to prevent the work from bending even if the punch touches the work.

In the above configuration, when the ram's own weight maximum drop speed calculation unit lowers the ram by its own weight, the notch hits the work. Calculate the maximum drop speed of the ram so that the workpiece does not bend even if it touches, and drop the ram so that the drop speed does not exceed the maximum drop speed of the ram.

Therefore, it is possible to prevent the work from being bent even when the notch hits the work due to the fall of the ram.

According to an eighth aspect of the present invention, there is provided a plate thickness detecting device for a press machine according to the invention, wherein a ram fitted with a punch is provided by a hydraulic cylinder operated by hydraulic oil from a bidirectional pump. A plate thickness detection device for a press machine that moves up and down to press a workpiece in cooperation with a punch and a die, including: a ram position detection device that detects the vertical position of the ram Means: Provided in the middle of a hydraulic circuit connecting the rod-side cylinder chamber of the hydraulic cylinder that moves up and down the ram and the bidirectional pump, and is discharged from the rod-side cylinder chamber. Hydraulic pressure detecting means for detecting the pressure of the operating oil; a judging unit for detecting the position at which the punch abuts on the workpiece from a change in the pressure of the hydraulic oil detected by the hydraulic pressure detecting means; Punch The thickness of the workpiece is calculated from the ram position when it is determined that the ram has contacted the workpiece and the height of the difference between the predetermined height of the ram and the upper surface of the die, which is known in advance. Department.

Therefore, in order to detect the upper surface position of the workpiece, which is the reference when detecting the thickness of the workpiece, the cylinder on the rod side of the hydraulic cylinder is moved up and down by the hydraulic pressure detecting means. Detects the pressure of the hydraulic oil discharged from the chamber, The judging section detects the position where the punch attached to the ram abuts the work from the change in the applied pressure, and the ram position detecting means detects the vertical position of the ram at this time. The change in the ram position is detected more sensitively than in the case of detecting the pressure in the cylinder chamber on the head side of the cylinder having a large cross-sectional area of the cylinder chamber. Then, when the upper surface of the work is detected, the plate thickness calculating unit predicts the work plate based on the set height of the difference between the predetermined height of the ram and the upper surface of the die. Calculate the thickness.

A plate thickness detecting device in a press machine according to a ninth aspect which is dependent on an eighth aspect, wherein the oil pressure detecting means is arranged in the middle of the hydraulic circuit. When the ram is lowered by its own weight by switching the speed switching valve provided in the pump to discharge the hydraulic oil from the load-side cylinder chamber to the bidirectional pump, and to lower the ram by its own weight It detects the pressure of hydraulic oil discharged from the side cylinder chamber.

In the above configuration, the ram fitted with the punch is lowered by its own weight and the speed switching valve is switched to reduce the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time. Pressure is detected by the pressure detecting means, and the change in the detected pressure is used to detect when the punch comes into contact with the work. While the ram is descending, there is no pressurized oil in the cylinder chamber on the head side of the cylinder, and the cylinder is sucked by the negative pressure generated by the lowering of the piston. ing.

Therefore, even if the detection of the contact of the nonch with the workpiece is delayed, only the weight of the ram or the like acts on the workpiece. Yes, it can prevent the work from bending.

According to a tenth aspect of the present invention, there is provided a plate thickness detecting device for a press machine according to the tenth aspect, which is dependent on the eighth or ninth aspect. When the punch touches the workpiece at the point when the pressure of the hydraulic oil discharged from the rod-side cylinder chamber detected from the pressure changes from the pressure due to its own weight to the atmospheric pressure It is determined.

Therefore, when the ram descends, the pressure of the hydraulic oil discharged from the rod-side cylinder chamber detected by the hydraulic pressure detecting means depends on the weight of the ram and the punch. Although the pressure is caused by the descent, the pressure due to its own weight disappears when the nonch contacts the work, so the hydraulic pressure detecting means detects the atmospheric pressure. Therefore, when the atmospheric pressure is detected, the determination section can determine that the nonch has contacted the workpiece.

The eighth or thirteenth aspect of the invention relates to the thickness detection in the press machine according to the eleventh aspect which is dependent on any one of the first aspects. The apparatus further includes: calculating a maximum falling velocity of the ram so as not to bend the work even when the nonch comes into contact with the work when the ram is lowered by its own weight. M The maximum weight drop speed calculation unit.

In the above configuration, the ram's own weight maximum drop speed calculation unit calculates the ram's own weight maximum drop speed so as not to bend the work even if the punch touches the work when lowering the ram by its own weight. Calculate and drop the ram so that the falling speed does not exceed the ram's own weight maximum falling speed.

Therefore, it is possible to prevent the work from bending even if the punch hits the work due to the fall of the ram.

A plate thickness detecting device for a press machine according to a twelfth aspect of the invention is a device for vertically moving a ram on which a punch is mounted, in cooperation with the punch and a die. A plate thickness detecting device for a press machine that performs evening press work, including the following: Detecting the position of the ram by lowering the ram by controlling the lowering speed from a certain height Ram position detecting means; a ram stop position is detected from a change in the ram position detected by the ram position means, and the detected stop position is brought into contact with the punch by the punch. A judging unit for judging the position; and a difference between a predetermined position and a predetermined height, which is determined in advance, and a ram position judged by the judging unit to be in contact with the punch. Calculate the work thickness from the set height Thickness calculation unit.

Therefore, in the above-described thickness detecting device, the ram is lowered from a certain height having a known height in order to detect the upper surface position of the work as a reference when detecting the thickness of the work. Then, the ram position is detected by the ram position detecting means, and the judging section detects the stop position from the detected change in the ram position, and judges that the stop position is the upper surface of the work. Detects changes in the ram position more sensitively than when detecting the pressure in the cylinder chamber on the head side, where the cross-sectional area of the cylinder chamber is large. be able to. Then, the plate thickness calculating unit can calculate the plate thickness of the work from the set height of the difference between the detected top surface position and the predetermined height of a predetermined ram and the top surface of the die, which is known in advance. . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a hydraulic circuit diagram and a control block diagram showing a plate thickness detecting device in a press machine according to the present invention.

FIG. 2 is a front view showing a press brake as a press machine according to the present invention.

FIG. 3 is a side view as viewed from the direction I II in FIG.

Figure 4 is a time chart showing the operation of the ram. FIG. 5 is a time chart showing the operation of the ram in the plate thickness detection method in the press machine according to the present invention.

FIG. 6 is an explanatory diagram for calculating the thickness of the work from the upper limit position of the upper table and the detected position of the upper surface of the work.

FIG. 7 is a hydraulic circuit diagram and a control block diagram showing another embodiment of the plate thickness detecting device in the press machine according to the present invention.

FIG. 8 is a flow chart showing another embodiment of the method for detecting the thickness of a press machine according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 2 and 3 show an entire hydraulic press brake 1 as an example of a press machine. The press brake 1 has side plates 3 L and 3 R erected on the left and right, and the upper table 5 U as a ram is vertically moved on the upper front end face of the side plates 3 L and 3 R. It has a lower table 5L fixed to the lower front surface of the side plates 3L and 3R, as well as being freely provided.

At the lower end of the upper table 5U, a punch P is provided to be exchangeable via an intermediate plate 7. A die D is provided at the upper end of the lower table 5L via a die base 9 so as to be exchangeable.

An example linear scale 11 is provided as a ram position detecting means for measuring the height position of the upper table 5U, and the height of the intermediate plate 7 and the punch P, which are already known, is provided. The distance from the die D can be determined using the distance.

Hydraulic cylinders 13L and 13R are provided on the upper front sides of the left and right side plates 3L and 3R, respectively, and the pistons 1 of these hydraulic cylinders 13L and 13R are provided. The upper tape 5U described above is attached to the lower end of the biston rods 17L and 17R mounted on 5L and 15R.

The hydraulic cylinders 13L and 13R have rod-side cylinder chambers 19 that detect the pressure of hydraulic oil discharged from the rod-side cylinder chambers 19. As an example, a hydraulic sensor 21 (see Fig. 1) is installed. The control device 23 that controls the hydraulic circuit of the press brake 1 It is provided adjacent to press brake 1.

Next, the hydraulic circuit of the hydraulic cylinders 13L and 13R and the control device 23 will be described with reference to FIG. Since the same hydraulic circuit is provided for the left and right hydraulic cylinders 13L and 13R, the right hydraulic cylinders 13R and 13R will be described below. The hydraulic circuit will be explained.

Hydraulic cylinder 13 for moving the upper table 5U, which is a ram, up and down The cylinder head 25 on the cylinder side of the cylinder R is a hydraulic pump via piping 27. Connected to one side of bidirectional pump 29. A pipe 31 is connected in the middle of the pipe 27 and is connected to an oil tank 35 via a check valve 33. The bidirectional pump 29 is operated by the servomotor 37. Further, the cylinder chamber 25 on the head side on the cylinder side is connected to the oil tank 35 by a pipe 39 through a prefill valve 40. A switching valve 41 is provided in the middle of the pipe 27, and the switching valve 41 is connected to an oil tank 35 via a pipe 42.

On the other hand, a pipe 43 is connected to the rod-side cylinder chamber 19 of the hydraulic cylinder 13 R, and a counterbalance valve 45 and a speed switching valve 47 are connected in parallel. It is provided in. The counterbalance valve 45 and the speed switching valve 47 are connected to the other side of the bidirectional pump 29 by a pipe 49, and are connected to the pipe 49 on the way. Pipe 51 is connected at This piping 51 is connected to an oil tank 35 via a check valve 53. The hydraulic sensor 21 for detecting the pressure of the hydraulic oil discharged from the rod-side cylinder chamber 19 is provided in the middle of the pipe 49.

According to the above configuration, when bending is performed, a thermopowder is used.

The bidirectional pump 29 is rotated in the forward direction by the rotation of 37, and the hydraulic oil is passed from the oil tank 35 through the check valve 53, the switching valve 41, and the pipe 27, and When it is supplied to the cylinder chamber 25 on the head side of the cylinder, the piston 15R is lowered, and the upper table 5U and the punch P are lowered. Hydraulic oil in the rod-side cylinder chamber 19 is returned to the bidirectional pump 29 via the pipe 43, the power supply valve 45, and the pipe 49, and similarly to the cylinder. Supplied to the cylinder side material 25 on the head.

On the other hand, when the bidirectional pump 29 is rotated in the reverse direction by the servomotor 37, the hydraulic oil flows from the oil tank 35 through the check valve 33 and the piping 49, and Speed switching valve

47 is supplied to the load side cylinder chamber 19 through the check valve of 7, and the piston rod 17 rises to raise the upper table 5U and the punch P.

The vertical position of the upper table 5U is detected by the linear scale 11. When the pressure in the cylinder chamber 19 on the opening side becomes higher than a predetermined value, the pre-fill valve 40 is opened by the pilot signal 55 and the cylinder is closed. The hydraulic fluid is directly sent to the oil tank 35 from the pressure side cylinder chamber 25 through the pre-fill valve 40. In the control device 23, an input means 59 such as a keyboard for inputting various data and an output means 61 such as a CRT for outputting various data are provided to a CPU 57 as a central processing unit. It is connected. The linear scale 11 and the oil pressure sensor 21 are connected, and the vertical position of the upper table 5U and the pressure of hydraulic oil discharged from the rod-side cylinder chamber 19 are measured. A detection signal has been sent.

In addition, a memory 63 that stores the input data and machining programs, a determination unit 65 that determines whether the punch P has contacted the workpiece W, and a punch P that stores A plate thickness calculator 67 that calculates the plate thickness of the work W from the position in contact with the work W, that is, the distance between the upper surface of the work W and the upper surface of the die D, is connected.

FIG. 4 shows a time chart showing the vertical movement of the upper table 5U and the state of the speed switching valve 47 with respect to the general operation of the upper table 5U and the punch P as a ram. I have. That is, the speed switching valve 47 is turned on to lower the upper table 5U at the upper limit position, and the speed switching valve 47 is turned off when the predetermined speed switching position is reached. From this point of time T until the upper table 5U reaches the lower limit position and rises, the hydraulic oil is sent from the bidirectional pump 29 to the cylinder chamber 25 on the cylinder side of the cylinder head. The hydraulic oil in the rod-side cylinder chamber 19 returns to the bidirectional pump 29 through the counterbalance valve 45. The switching valve 41 is on during the time T. On the other hand, Fig. 5 shows the vertical movement of the upper table 5U, the state of the pressure in the speed switching valve 47 and the pressure in the rod-side cylinder chamber 19 in the plate thickness detection method according to the present invention. Is shown.

Here, the cross-sectional area of the rod-side cylinder chamber 19 is smaller than the cross-sectional area of the cylinder-head cylinder chamber 25 (for example, about 1:10). Paying attention to the fact that the pressure of the hydraulic oil discharged from the rod-side cylinder chamber 19 is sensitive, it is discharged from the rod-side cylinder chamber 19 Monitor the hydraulic oil pressure (bottom row in Fig. 5).

First, the speed switching valve 47 is turned on at a fixed height position at which the height is known, for example, at the upper limit position, and the upper table 5U starts to descend rapidly, and reaches the predetermined speed switching position. — The discharge amount of the bidirectional pump 29 is reduced by the control of the boom 37 and switched to the bending operation. Then, upon detecting contact with the workpiece W, the speed switching valve 47 is turned off.

Since the cylinder chamber 25 on the head side of the cylinder is not pressurized and the screw 15 descends due to the weight of the upper table 5U and the punch P, etc., the cylinder head 25 is lowered. Hydraulic oil is sucked into the load-side cylinder chamber 25 by negative pressure, and the hydraulic oil in the rod-side cylinder chamber 19 is discharged. Accordingly, the hydraulic sensor 21 detects the pressure due to its own weight of the upper table 5U and the punch P until the punch P comes into contact with the work W, and the hydraulic sensor 21 contacts the work W. When touched, piston 15 drops As the pressure stops, the pressure drops at once to reach atmospheric pressure. When the pressure in the cylinder chamber 19 on the rod side reaches the atmospheric pressure, the judging section 65 judges that the punch P has come into contact with the work W, and the upper part of this time is determined. The height position HI of the table 5U is detected by the linear scale 11 and the plate thickness calculating section 67 stores the upper limit position of the upper table 5U and the die D which are stored in the memory 63 in advance. The height d of the work W is calculated from the difference H 0 between the height to the upper surface position of the work table and the height position HI of the upper table 5 U by d = H 0 — HI (Fig. 6 reference).

Then, the speed switching valve 47 is switched off, and at the same time, hydraulic fluid is supplied to the cylinder chamber 25 on the head side of the cylinder, and the work W is pressed according to the calculated plate thickness. Processing starts.The hydraulic oil in the rod-side cylinder chamber 19 is returned to the bidirectional pump 29 through the counterbalance valve 45, so that both hydraulic sensors 21 It becomes the suction pressure of the pump 29.

Based on the above results, the upper table 5U is lowered by its own weight, such as the upper table 5U and the punch P, and the load-side cylinder chamber 19 when the upper table 5U is lowered 19 The change in pressure to the negative side of the valve is detected, and the time when the punch P comes into contact with the work W is detected from the change in the pressure.Therefore, even when the detection speed is low, the switching valve 41 is turned off. As the oil escapes to the oil tank 35, the oil is turned on after the detection of the thickness, and the oil is supplied to the cylinder chamber 25 on the head side of the cylinder. Since the bending load is not applied to the work W, the deformation of the work W can be prevented. The rod-side cylinder chamber has a small cross-sectional area. Since the judgment is made based on the pressure of 19, the judgment can be made more accurately.

Next, when the upper table 5U was dropped by its own weight as described above, A method of controlling the ram's own weight falling speed when the workpiece W may be bent when the workpiece P contacts the workpiece W, for example, when the workpiece W is thin or the bending length is short is described.

Referring to FIG. 7, in the control device 69 in this case, a ram own weight maximum drop velocity calculation unit 71 is additionally provided to the control device 23 shown in FIG. Since other configurations are the same as those shown in FIG. 1, common portions are denoted by the same reference numerals, and overlapping description will be omitted.

The ram's own weight maximum drop velocity calculation unit 71 calculates the punch P and the work W by dropping the upper table 5U from the input work conditions and the weight of the upper table 5U and the punch P, which are already known. This is to calculate the maximum falling speed of the upper table 5 U etc. by its own weight so as not to bend the work W when it comes into contact with the object.

With reference to FIG. 8, a description will be given of a method of detecting a plate thickness by such a control device 69. First, after the start (Step SS), the work conditions such as the nominal thickness of the work W, the bending length, and the tensile strength of the work are input from the input means 59 (Step S1). The ram's own weight maximum drop velocity calculation unit 71 drops the ram's own weight from the ram's own weight, which is the own weight of the upper table 5 U and punch P, etc. Calculate the speed (step S2).

That is, the maximum value of the ram's own weight falling speed (that is, bending speed) that satisfies the following equation (1) may be obtained.

Bending pressure required for bending = f (Nominal workpiece thickness, bending length, tensile strength)> Ram Weight (t on) X Bending speed (mm Z s) …… (1)

Then, the upper table 5U is lowered by its own weight at its own weight falling speed that does not exceed the calculated ram maximum own weight falling speed (step S3). Here, as a method of adjusting the ram's own weight drop speed so as not to exceed the ram's maximum own weight drop speed, the switch valve 41 on the head side of the bidirectional pump 29 is turned off and the cylinder is turned off. This can be achieved by connecting the cylinder chamber 25 on the head side of the cylinder to the tank 35 and controlling the rotation speed of the bidirectional pump 29. Alternatively, if the bidirectional pump is not used, the solenoid proportional valve for ascent / descent switching is switched to the descent process, and the spool opening / throttle control is finely controlled. Can be.

In this way, the ram descends at the maximum falling speed of its own weight, and when the ram reaches the predetermined speed switching position in the same manner as in the above-described embodiment, the speed switching valve 47 is switched (step S4), and the rod side When the pressure in the cylinder chamber 19 becomes the atmospheric pressure, the judging section 65 judges that it has come into contact with the punch P force work W (step S5).

Referring to Fig. 6, the position of the upper table 5U at this time is shown. HI is detected by the linear scale 11, and the thickness calculating unit 67 calculates the height between the upper limit position of the upper table 5 U and the upper surface position of the die D stored in the memory 63 in advance. The thickness d of the work W is calculated from the difference H 0 from d = H 0 — HI (step S 6). At this time, the switching valve 41 is turned ON, and the bidirectional pump 29 is operated to supply hydraulic fluid to the cylinder chamber 25 on the head side of the cylinder.

Calculate the D value for bending the workpiece to the predetermined angle with respect to the detected workpiece thickness d (step S7), and detect the upper table 5 by the linear scale 11 Until the U position reaches the calculated D value (step S8), the upper table 5U is lowered (step S9), and the pressurizing operation is completed (step SE).

From the above results, for example, when the work W is thin or the bending length is short, the upper table 5U is dropped by its own weight, such as the upper table 5U and the punch P, and is brought into contact. Since the ram falls at a speed that does not exceed the maximum falling speed of its own weight, the thickness of the workpiece W can be reduced in the shortest time without bending the workpiece W when the nonch P contacts the workpiece W Detection can be performed. In addition, the use of this sheet thickness detection method for bending can shorten the bending time.

This invention is not limited to the above-described embodiment of the invention, but can be embodied in other forms by making appropriate changes. That is, the fruit of the invention described above In the embodiment, the press brake 1 has been described as a press machine, but the present invention can be applied to other press machines as well.

Further, the ram is lowered from a certain height position where the height is known, the ram position is detected by the ram position detecting means, and the ram is lowered from the detected ram position. The stop position is judged by the judging unit to be that the punch has contacted the work, and the sheet thickness calculating means determines the stop position of the ram at this time and a certain height of the ram that is known in advance. The work thickness can be determined from the height and the set height from the die top surface. The stop of the descent of the ram is detected from the change in the ram position detected by the ram position detection means, but also from the deviation between the detected ram position and the command value. It can also be detected.

Claims

The scope of the claims

1. A method for detecting thickness in a press machine, including the following steps:

Lowering the ram from a certain height;

Detecting the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time;

Detecting when the punch touches a workpiece on the die from the detected change in pressure;

Detect the vertical position of the ram at this time;

Calculating the thickness of the work from the detected position of the height of the ram, the predetermined height of the pressure which is known in advance, and the set height of the upper surface of the die; and

Based on the thickness of the work thus obtained, the work on the work is subjected to press working in cooperation with the die and the die by vertically moving the ram on which the punch is mounted.

2. In the method for detecting a thickness of a press machine according to claim 1,

Lowering the ram by its own weight;

Detecting the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time; and

Detects when the punch comes into contact with the work from the detected pressure change.

3. In the method for detecting a thickness of a press machine according to claim 2,

When the ram is lowered by its own weight, it is lowered at a speed equal to or lower than the ram's own weight maximum drop speed so that the work does not bend even if the punch comes into contact with the work.

4. In the method for detecting a thickness of a press machine according to claim 3,

The point at which the pressure of the hydraulic oil discharged from the rod-side cylinder chamber changes from the pressure due to its own weight to the atmospheric pressure is detected as the time when the punch abuts on the work.

5. The method of detecting the thickness of a press machine includes the following steps:

Controlling the descending speed of the ram from a certain height to detect the descending position of the ram;

Detecting the stop position of the ram from the detected change in the ram position;

Judging the detected stop position as a position at which the punch abuts a work on the die;

The thickness of the work is determined from the ram position determined to be in contact with the work and the set height of the difference between the predetermined height and the upper surface of the die, which is known in advance; and

The ram with the punch is moved up and down based on the thickness of the workpiece as determined above, and the punch and the die cooperate with each other. Press the work.

6. The thickness detecting device in the press machine includes: a ram position detecting means for detecting a vertical position of a ram mounted with a punch;

Hydraulic pressure detecting means for detecting a pressure of hydraulic oil discharged from a rod-side cylinder chamber of a hydraulic cylinder moving up and down the ram;

A judging unit for detecting a position at which the punch abuts on the workpiece from a change in pressure detected by the oil pressure detecting means;

Setting of the difference between the ram position at the time when the judgment unit judges that the punch has contacted the work, a certain height of the ram known in advance, and the top surface of the die A sheet thickness calculator for calculating a sheet thickness from the height;

Thus, the ram is moved up and down by the hydraulic cylinder, and the work is pressed by the cooperation of the punch and the die.

7. The apparatus for detecting the thickness of a press machine according to claim 6 further includes:

When the ram is lowered by its own weight, a ram own weight maximum drop speed calculation unit that calculates a ram own weight maximum drop speed that does not bend the workpiece even if the punch abuts on the workpiece.

8. In the plate thickness detecting device of the press machine, the ram fitted with the punch is moved up and down by the hydraulic cylinder operated by the hydraulic oil from the bidirectional pump. A plate thickness detecting device for a press machine that presses a work in cooperation with a punch and a die, including: a ram position detecting means for detecting a vertical position of the ram; The hydraulic cylinder, which moves up and down the ram, is provided in the middle of a hydraulic circuit connecting the rod-side cylinder chamber of the hydraulic cylinder and the bidirectional pump, and is discharged from the cylinder chamber of the port-side cylinder. Hydraulic pressure detecting means for detecting the hydraulic oil pressure;

A judging section for detecting a position at which the punch abuts on a work from a change in pressure of the hydraulic oil detected by the hydraulic pressure detecting means;

The setting height of the difference between the ram position at the time when the punch has come into contact with the work by the judgment unit and a predetermined height of the ram and the upper surface of the die, which is known in advance. A sheet thickness calculator that calculates the work thickness from the work.

9. A thickness detecting device for a press machine according to claim 8,

The hydraulic pressure detecting means switches a speed switching valve provided in the middle of the hydraulic circuit, discharges hydraulic oil from the rod-side cylinder chamber to the bidirectional pump, and sets the ram to its own weight. It detects the pressure of the hydraulic oil discharged from the rod-side cylinder chamber when it is lowered further.

10. In a plate thickness detecting apparatus for a press machine according to claim 9, wherein the judging section detects a position from the rod-side cylinder chamber detected by the hydraulic pressure detecting means. The point in time when the pressure of the discharged hydraulic oil changes from the pressure due to its own weight to the atmospheric pressure is determined as the time when the punch abuts the peak.

11. The thickness detecting device for a press machine according to claim 10 further includes:

When the ram is lowered by its own weight, a ram own weight maximum drop speed calculation unit that calculates a ram own weight maximum drop speed that does not bend the work even if the punch abuts on the workpiece.

1 2. The thickness detection device in the press machine, which moves the ram on which the punch is mounted up and down, and presses the work in cooperation with the punch and die described above. An apparatus, comprising: a ram position detecting means for detecting a lowered position of the ram by lowering the ram from a certain height position by controlling a lowering speed;

A ram stop position is detected from a change in the ram position detected by the ram position means, and the detected stop position is determined. A determining unit for determining that the punch has contacted the work; and a ram position at which the determining unit determines that the punch has contacted the work, and the predetermined height that is known in advance. A thickness calculator that calculates the thickness of the workpiece from the set height of the difference between the die and the top of the die.